The present invention relates to systems for diagnosing and controlling an ignition system of an internal combustion engine, and more specifically to such systems for detecting and logging predetermined ignition system failure modes as they occur and for controlling the ignition system in accordance with ignition system abnormalities.
In electronic controls for internal combustion engines, it is known to electronically determine and control timing events associated with the engine ignition system in order to properly ignite air-fuel mixtures supplied to the engine. Typically, an engine control computer is responsive to crankshaft angle, engine coolant temperature, commanded engine fueling, intake air temperature and other engine operating conditions to produce appropriate firing command signals for generating high voltage sparks at a number of spark plugs, thereby resulting in combustion of the air-fuel mixture.
In the operation of a typical internal combustion engine ignition system, the engine control computer determines in a conventional manner an appropriate time to energize the primary side of an ignition coil associated with the engine (hereinafter referred to as a xe2x80x9cfiring commandxe2x80x9d). At that time, current begins to flow from a voltage source, such as a vehicle battery through the coil primary.
While the Muth et al. system is operable to distinguish between a normally operating ignition system and a misfire condition, it has several drawbacks associated therewith. For example, while it may effectively detect one or more misfire conditions, the Muth et al. system does not distinguish between any of the various possible ignition system failures. Thus, the Muth et al. system is incapable of providing any information relating to a particular cause of the misfire condition. Moreover, since the Muth et al. system is not operable to determine the cause of the misfire condition, it cannot properly use the misfire information to alter ignition and/or fuel strategies in real time to thereby minimize the effect of a particular cause of the misfire condition.
What is therefore needed is a system for diagnosing and controlling an ignition system of an internal combustion engine, wherein such a system is operable to detect, and distinguish between, a number of possible ignition system failure modes. Such a system should include at least the capability to store information relating to the types and number of occurrences of all ignition system failure modes which have occurred for later analysis, and should ideally be further capable of utilizing the information relating to any presently occurring ignition system failure mode to alter engine fueling, spark timing and/or spark energy during a subsequent firing command to thereby at least minimize the effect of the failure condition on proper engine operation.
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for detecting ignition system failures comprises an ignition coil having a primary coil coupled to a secondary coil, means for energizing the primary coil to thereby induce a spark voltage in a high tension side of the secondary coil, a voltage sensor associated with the high tension side of the secondary coil, the voltage sensor sensing the spark voltage and producing a spark voltage signal corresponding thereto, and a computer having an input receiving the spark voltage signal. The computer analyzes the spark voltage signal and determines therefrom whether the spark voltage signal corresponds to an ignition system failure.
In accordance with another aspect of the present invention, a system for detecting ignition system failures, comprises an ignition coil having a-primary coil coupled to a secondary coil, means for energizing the primary coil to thereby induce a spark voltage in a high tension side and an ion voltage in a low tension side of the secondary coil, an ion sensor associated with the low tension side of the secondary coil, the ion sensor sensing the ion voltage and producing an ion voltage signal corresponding thereto, and a computer having an input receiving the ion voltage signal.
The computer analyzes the ion voltage signal and determines therefrom a combustion quality value associated with the spark voltage.
In accordance with a further aspect of the present invention, an apparatus for diagnosing ignition system failures comprises an ignition coil having a primary coil coupled to a secondary coil, means for energizing the primary coil to thereby induce a spark voltage signal in the secondary coil, and a first computer having an input coupled to the secondary coil for receiving the spark voltage signal. The computer includes a first memory having at least one spark voltage waveform stored therein corresponding to a spark voltage signal of a predefined ignition system failure mode, and the computer compares the spark voltage signal with the at least one spark voltage waveform and produces a diagnostic signal corresponding to a predefined ignition system failure mode if the spark voltage signal matches the at least one spark voltage waveform.
In accordance with yet another aspect of the present invention, an apparatus for predicting ignition system failures, comprises an ignition coil having a primary coil coupled to a secondary coil, a spark plug connected to a high tension side and to a low tension side of the secondary coil and defining a spark gap therebetween, an ignition control circuit connected to the primary coil and having an input responsive to a firing command to energize the primary coil to thereby induce a spark voltage in the high tension side of the secondary coil and a corresponding spark in the spark gap, the spark voltage exhibiting a voltage peak having a peak value corresponding to a breakdown voltage of the spark gap, and a first computer having an input coupled to the high tension side of the secondary coil for receiving the spark voltage. The first computer compares the peak value of the voltage peak with a threshold value and produces a prognostic signal corresponding to a predefined ignition system failure mode if the peak value is greater than the threshold value.
In accordance with still another aspect of the present invention, an apparatus for predicting ignition system failures, comprises an ignition coil having a primary coil coupled to a secondary coil, a spark plug connected to a high tension side and to a low tension side of the secondary coil and defining a spark gap therebetween, an ignition control circuit connected to the primary coil and having an input responsive to a firing command to energize the primary coil to thereby induce a spark voltage in the high tension side of the secondary coil and a corresponding spark in the spark gap, the spark voltage exhibiting a voltage peak having a peak value corresponding to a breakdown voltage of the spark gap, and a first computer having an input coupled to the high tension side of the secondary coil for receiving the spark voltage. The first computer compares a slope of the voltage peak about the peak value with a predefined slope value and produces a prognostic signal corresponding to a predefined ignition system failure mode if the slope of the peak value is less than the predefined slope value.
In accordance with yet a further aspect of the present invention, an apparatus for diagnosing ignition system failures comprises an ignition coil having a primary coil coupled to a secondary coil, a spark plug connected to a high tension side and to a low tension side of the secondary coil and defining a spark gap therebetween, an ignition control circuit connected to the primary coil having an input responsive to a firing command to energize the primary coil to thereby induce a spark voltage in the high tension side of the secondary coil and a corresponding spark in the spark gap, the spark voltage exhibiting a voltage peak having a peak value corresponding to a breakdown voltage of the spark gap, and a first computer having an input coupled to the high tension side of the secondary coil for receiving the spark voltage. The first computer determines a spark energy of the spark as a function of the peak value of the voltage peak and provides a spark energy correction signal as a function of the spark energy. The ignition control circuit is responsive to the spark energy correction signal to alter a spark energy of the spark induced in the spark gap.
In accordance with still a further aspect of the present invention, an apparatus for diagnosing ignition system failures comprises an ignition coil having a primary coil coupled to a secondary coil, means for energizing the primary coil to thereby induce a spark voltage in a high tension side of the secondary coil and an ion voltage in a low tension side of the secondary coil, a fueling system responsive to a fueling command signal to fuel an internal combustion engine, a first computer providing the fueling command signal to the fueling system, and a second computer having an input coupled to the low tension side of the secondary coil for receiving the ion voltage and a first output connected to the first computer. The second computer processes the ion voltage and determines a combustion quality value therefrom, and compares the combustion quality value with a first threshold value and provides a first fueling command correction signal at the first output if the combustion quality value exceeds the first threshold value. The first computer is responsive to the first fueling command correction signal to alter the fueling command signal to thereby decrease fuel supplied to the engine.
In accordance with yet a further aspect of the present invention, an apparatus for diagnosing ignition system failures comprises an ignition coil having a primary coil coupled to a secondary coil, means for energizing the primary coil to thereby induce a spark voltage in a high tension side of the secondary coil and an ion voltage in a low tension side of the secondary coil, a fueling system responsive to a fueling command signal to fuel an internal combustion engine, a first computer providing the fueling command signal to the fueling system, and a second computer having an input coupled to the low tension side of the secondary coil for receiving the ion voltage and a first output connected to the first computer. The second computer processes the ion voltage and determines a roughness value therefrom, compares the roughness value with a roughness threshold and provides a fueling command correction signal at the first output if the roughness value exceeds the roughness threshold. The first computer is responsive to the fueling command correction signal to alter the fueling command signal to thereby decrease fuel supplied to the engine.
One object of the present invention is to provide an ignition system for an internal combustion engine wherein the high tension side of the secondary winding of the ignition coil includes a spark voltage sensor.
Another object of the present invention is to provide an ignition system for an internal combustion engine wherein the low tension side of the secondary winding of the ignition coil includes an ion voltage sensor.
Yet another object of the present invention is to provide a diagnostic apparatus for an ignition system operable to sense spark voltage in the high tension side of the secondary winding of the ignition coil and compare the sensed spark voltage with a number of predefined spark voltage waveforms stored in memory to thereby determine whether the sensed spark voltage is exhibiting any of a number of predefined ignition system failure modes.
Still another object of the present invention is to provide a diagnostic apparatus for an ignition system operable to sense a voltage peak of the spark voltage in the high tension side of the secondary winding, wherein the voltage peak corresponds to the breakdown voltage of the spark gap of the spark plug, compare the voltage peak with a threshold peak, and store a corresponding prognostic failure code within memory whenever the peak voltage exceeds the threshold peak.
A further object of the present invention is to provide such a system operable to determine a slope of the spark voltage about the voltage peak and store a corresponding prognostic failure code within memory whenever the slope of the voltage peak is less than a predefined slope.
Still a further object of the present invention is to provide such a system operable to determine a spark energy as a function of the value of the voltage peak and alter the firing command timing (spark timing) to thereby induce a minimum spark energy in the spark gap, wherein the minimum spark energy corresponds to that required to establish breakdown in the gap and reliable ignition of the air/fuel mixture.
Yet a further object of the present invention is to provide a diagnostic apparatus for an ignition system operable to sense an ion voltage in the low tension side of the secondary winding of the ignition coil, process the ion voltage to determine a combustion quality value therefrom and alter an engine fueling command, firing timing command (spark timing) and/or spark energy if the combustion quality value is outside a predefined range of acceptable combustion quality values, and log a misfire error code in memory if the combustion quality value is below a misfire threshold value.
Still a further object of the present invention is to provide a diagnostic apparatus for an ignition system operable to sense an ion voltage signal in the low tension side of the secondary winding of the ignition coil, process the ion voltage signal to determine a roughness value thereof during a predefined time duration after an occurrence of peak cylinder pressure and alter an engine fueling command, firing command timing (spark timing) and/or spark energy if the roughness value exceeds a predefined roughness threshold value.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiments.